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. .( . ~iO 0 3 a gradient of 8.to 10 feet per mile on the plains area. Many of the tributaries draining the plains have steeper gradients, from l~ to 70 feet per mile. The South Platte River Basin is bounded by the North Platte Basin on the north, by the Republican River tributaries on the east and south, and in its upper reaches by the Arkansas River Basin on the south. The climate of the area included in the Narrows Unit is charac- teristic and similar to that in the western Great Plains. The region is normally semi-arid although precipitation varies \olidely from year to year. Both temperature and precipitation are influenced by the great air masses and weather fronts which sweep across the Great Plains Province. Temperate weather with abnndant sunshine, warm clear days and cool nights during the growing season make the area especially favor- able for agriculture and its associated industries. Although natural precipitation is adequate to support only highly speculative dryland farming and livestock grazing, a wide variety of crops with high yields may be grown when irrigation water is sufficient. Temperatures in the area have ranged from a high of 109 degrees F. to minus ~l degrees F. Average January and July temperatures for three representative stations in the basin are shown in Table 3. Precipitation is greatest in the eastern part of the unit and gradually diminishes from east to west. The four month period, November thrmlgh February, is the driest part of the year. Less than one-half inch of moisture is normally received during each of these four months. April, Hay, June, and July are the wettest months during which more than one-half of the annual precipitation is received. After May, precipi- tation decreases as the summer progresses. Table 3 also presents precipitation data for three stations in the conservancy district: Table 3.--Climatologic data for lower South Platte River Basin Temperature Annual Precipitation (degrees F.) (inches) Station County ;>" Highest Lowest " (j) ,H ><: " '" > '" 'rl recorded recorded Average h<:t. hc::r' '5' '5' Julesburg Seq.g\olick 27.7 76.4 109 -38 37.07 7.75 16.32 Sterling Logan 24.8 73.9 106 -33 22.25 7.27 1l+.10 Ft. Morgan Morgan 24.3 73.9 109 -~l 26.51 6.41 12.86 17 .."